One of the latest safety devices for vehicles is the Adaptive Front-lighting System (AFS) which allows the head light turns according to needs and the system includes a driving device to turn the head light. A latest driving device known to applicant includes step motor and a sensor connected to the output shaft of the motor, wherein the sensor detects the angle that the output shaft rotates and generates a reference voltage which is compared with a pre-set voltage so as to decide the position of the head light. A control unit is then activate the step motor to rotate the output shaft of the step motor to move the head light to pre-set position. Although errors from the parts or the environment have been considered by the known device, the range of the pre-set voltage does not include method for detecting errors. Therefore, the drivers cannot correct the movement of the head light when errors that are not considered by the device happen. In other words, if the driving device of the head light cannot work functionally and the driving device cannot correct the errors, the drivers take risks to drive.
The present invention intends to provide a method for driving the driving device of the head light and the method provides a detection function to detect errors of the movement of the head light.